Voltage opinion....

[playonit]

Would you guys mind checking my 5e7 voltage chart attached and offering some feedback?... My voltages seem to run high compared to the chart supplied on the Ceriatone site. I built the amp from scratch using Magnetic Components PT rated at 710v . my measurements are highlighted... on v2 and v3 they seem to run around 20v high and B+ running over 400v ... Also on pins 6 on v4 and v5 I am seeing neg v is the chart wrong or am I missing something... I wanted to wait to ask since I was using a $40 RSHACK DMM and wasn't trusting it. Today I received my new Amprobe 37XR-A meter and still seeing the high volts so it doesn't appear to be the meter...... Thanks Guys.......

[Bob-I]

What's your wall voltage? My typically runs a tad high so I see voltages in the amps a tad high as well. Hasn't hurt anything in my amps.

Just make sure you bias correctly for the voltages and you'll be fine. These voltage are not out of spec for 6L6 amps at all.

[playonit]

What's your wall voltage? My typically runs a tad high so I see voltages in the amps a tad high as well. Hasn't hurt anything in my amps.

Just make sure you bias correctly for the voltages and you'll be fine. These voltage are not out of spec for 6L6 amps at all.

What if I am running 5881's ??

[ToneMerc]

Well, original line voltage was only 110v vs todays 120v+ for starters. That transformer HT (355) is too high for 5E7 period correct voltages. True 5E7 voltages are only 140V on both V1& V2 plates and around 395-410V on the OT plates. I would knock the voltages down, it ain't a 5E7 without the correct lower voltages.

You build V2 as a cathode follower correct?

The first thing I would do would be to pull that 5U4 and drop in an NOS 5R4, this should knock your B+ down 15-18V or so. A 5Y3 should knock your B+ down maybe 10-12v, which would be a great start. However, a 5Y3 has about half the current capability of an 5U4. Now you might be able to get by with NOS 5Y3 for casual bedroom plinking, but if you are going to lean on it definitely a 5R4.

good luck

TM

[Structo]

A 5U4 drops around 45-50 volts

A 5Y3 drops around 60 volts

A 5AR4 only drops around 17-20 volts

[David Root]

5R4, not 5AR4, Tom. Big difference.

[ToneMerc]

Tom, I assumed that he has a 5U4 in it now, installing the 5Y3 or 5R4 will additionally drop it around those voltages I referenced. He doesn't need to install a 5AR4 as the voltages will increase.

TM

[Structo]

Oops, sorry misread

[playonit]

Will leaving it as is (5U4G) with the 5881's instead of 6L6's shorten the life of tubes substantially? Amp sounds very nice.. I was just concerned about the higher B+ voltage ... My first built 5e7 with Weber transformers is 388v... same Fender equivalent (022798) as the MC PT but with (HT) 360V..

[Bob-I]

Depends on the 5881, what brand/vintage?


In general, there should be no problem. Leo ran 5881's in the good ol' 5F6-A at over 400V with no problem.

[playonit]

Depends on the 5881, what brand/vintage?


In general, there should be no problem. Leo ran 5881's in the good ol' 5F6-A at over 400V with no problem.

5881's Tung-Sol re-issues.. the 12ax7's are NOS Brimar the 12ay7 is Nos Jan/GE and the 5U4G is a Raytheon...

Thanks Bob... I will leave as is... sounds good, ain't smokin... so I ain't

[FYL]

Would you guys mind checking my 5e7 voltage chart attached and offering some feedback?

Voltages are quite high but can be typical of modern PTs used on 120+ volts. The amp will be fine provided that you add screen limiting resistors - typically 470R / 3W per tube.

Bias seems quite cold, with 5881s drawing too little current and contributing to the highish voltages. With 420 V plates, shoot for app. 40 to 45 mA plate current, which would translate into approximately -38 to -40 V bias voltage.

[FYL]

In general, there should be no problem. Leo ran 5881's in the good ol' 5F6-A at over 400V with no problem.

All medium and large octals can run at 500V plate, provided that screens are held tight and that max dissipation isn't exceeded. Even small 6V6GTs are really happy with 450+ volts!

[Bob-I]

Depends on the 5881, what brand/vintage?


In general, there should be no problem. Leo ran 5881's in the good ol' 5F6-A at over 400V with no problem.

5881's Tung-Sol re-issues.. the 12ax7's are NOS Brimar the 12ay7 is Nos Jan/GE and the 5U4G is a Raytheon...

Thanks Bob... I will leave as is... sounds good, ain't smokin... so I ain't

They'll handle it for sure. Leave it alone and rock, do some Townsend power chords ala Won't get fooled.

[dynaman]

In general, there should be no problem. Leo ran 5881's in the good ol' 5F6-A at over 400V with no problem.

All medium and large octals can run at 500V plate, provided that screens are held tight and that max dissipation isn't exceeded. Even small 6V6GTs are really happy with 450+ volts!

Amen, and I tip my beer to another feller that shows zero restraint in regards to operating voltages!

The last Sovtek 5Y3 I purchased didn't drop squat for voltage, so I wound up with 475V+ on the plates and screens of a pair of JJ 6V6s. Tubes are still running strong more than a year later. Me thinks I got a relabeled 5AR4.

Incidentally, I've made a mental note to never purchase used tubes from you.